1. Field of the Invention
The invention relates to a safety lock with at least one lock catch and a bolt, which is operable by means of a lock cylinder and a split latch nut, the split latch nut having an inner nut with a panic function and an outer nut with a freewheel function, which can be coupled by means of an electromagnetic coupling device.
2. Discussion of the Background
A lock according to the preamble is also known from DE 44 07 244 C1. A bolt of this lock is operable by means of a latch nut or a lock cylinder. The latch nut is in two parts in order to ensure in the case of a panic situation that opening by means of an inner door knob. An inner or panic nut is connected in non-rotary manner to a latch lever, which by means of drivers can move a lock catch and by means of a pivot lever a bolt from an extended closed position into a retracted open position. An outer nut connected in non-rotary manner to the outside door knob can be connected by means of an electromagnetically operable coupling to the inner nut. The coupling device comprises a spring-tensioned detent, as well as an electromagnet armature used for detent actuation purposes. If the electromagnet is unenergized, the levers of the inner and outer nut are decoupled, whereas when the electromagnet is energized the detent leads through the attracted armature to the coupling of the inner and outer nut lever.
The known coupling device is advantageous for locks subject to no significant limitations with regards to their dimensions and in particular their width. For framed doors having a relatively narrow area for the installation of a lock and which must also comply with the insurance law regulations concerning the bolt move out in a locking position, the known coupling device is less suitable as a result of its dimensions. In addition, differently constructed nut levers are used, so that a more rational manufacture and installation is only possible to a limited extent.